1. Field of the Invention
The invention relates generally to the field of networks. More particularly, the invention relates to asynchronous transfer mode networks. Specifically, a preferred implementation of the invention relates to a multi-link segmentation and reassembly sublayer for bonding asynchronous transfer mode permanent virtual circuits.
2. Discussion of the Related Art
Asynchronous transfer mode (ATM) is a popular technology for providing secure and reliable virtual private network (VPN) arrangements. The use of ATM technology allows the sharing of access and inter-machine trunks by multiple logical links. The underlying premise of ATM is that a data stream can be segmented into, cells. The ATM standard calls out for cells that contain 48 bytes of user data. Appended to each cell are 5 bytes of overhead that include an identifier of the destination. This identifier is encapsulated as a combination of Virtual Path Identification (VPI) and Virtual Channel Identification (VCI). Connections are performed by the ATM Switches on a cell-by-cell basis, using the VPI/VCI as a pointer to match the ingress and egress trunks from an ATM switch. A permanent virtual circuit (PVC) is established by provisioning the intervening ATM switches between the two (or more) points of customer (end-user) access into an ATM cloud. All ATM cells have a prescribed VPI/VCI in the cell-overhead when launched from a given location. The 48 bytes of user-data are transported across the ATM cloud, though the overhead may be modified. Cells associated with a specific PVC traverse the same route.
Problems associated with current ATM technology includes bandwidth constraints, which can represent a significant limitation. A point-to-point bandwidth increase with an inherent flexibility in data volume transfer is what is needed.
One unsatisfactory approach, in an attempt to solve this bandwidth constraint problem involves a method for inverse multiplexing over ATM (IMA). IMA is a standardized method that provides bonding of multiple low-speed physical links to emulate a high-speed logical link. A drawback of the IMA approach is that it requires that all of the low-speed physical links to have the same bit-rate. However, especially during times of network congestion, low-speed physical links may not present the same bit-rates. A network may often have available multiple physical links of different bit-rate capacities. What is needed is a solution that bonds multiple low-speed physical links that do not have the same bit-rate capacities. Heretofore, the requirement of bonding multiple low-speed physical links where the multiple low-speed physical links do not have the same bit-rate capacities has not been fully met.